In many types of machines different tools are coupled to and then uncoupled from the machine to accomplish different tasks. For example, a hoe excavator with a hoe arm may have a variety of buckets of various widths and shapes that are suitable for particular different tasks. Depending on the task, the desired bucket is coupled to the end of the hoe arm of the excavator, and when that task is finished the bucket will be uncoupled and a different bucket will be coupled to the arm to accomplish the next task. In addition to various buckets, other tools such as pneumatic hammers, post hole augers, and the like are often attached to the excavator arm to increase the variety of tasks that the machine may accomplish.
Changing the bucket can be time consuming and so various quick coupling mechanisms have been developed to reduce the time and effort required to couple various tools to the excavator arm. Often these tools are maneuvered in holes or like confined areas where people are working, and so it is necessary for such quick coupling mechanisms to secure the tool such that the tool cannot fall off accidentally, and further must secure the tool tightly to the end of the excavator arm such that undesirable loose movement of the tool with respect to the excavator arm is prevented and control is maintained.
U.S. Pat. No. 6,487,800 to Evans et al. discloses a quick coupler with a coupling bar that is moved by rotating threaded bolts to a closed and coupled position to secure the engagement of the end of an excavator arm to a tool, such as a bucket. U.S. Pat. Nos. 5,890,871 to Woerman and 7,654,019 to Yeager et al. disclose quick coupler mechanism where a spring exerts a bias force on a wedge shaped bar towards a closed position where the bar is engaged in a groove to lock the tool to the arm. When pressurized fluid is directed into a single acting hydraulic cylinder, the cylinder exerts a force against the bias force of the spring to move the bar to the open position where the bar is disengaged from the groove. When the pressurized fluid is released from the cylinder, the bias force collapses the cylinder and moves the bar to the closed position. Thus if the hydraulic cylinder fails, the bar stays closed, engaging the tool and arm so the tool does not fall off.
The present quick coupler mechanisms are designed for conventional large excavators and the like. More recently very much smaller versions of these machines, commonly referred to as mini-excavators, have become popular and scaling down the existing quick couplers for use on these mini excavators has been problematic. In the coupler mechanisms of Woerman and Yeager, the hydraulic cylinder extends from the bar towards the closed position, and thus inside the coupler mechanism. This arrangement works well where there is considerable room, as in conventional large excavators and the like, but is problematic where the mechanism is scaled down for a mini excavator.